(i) Field of the Invention
This invention relates to heat regulating units for forced air heating systems.
(ii) Description of the Related Art
It is known to recover heat from the flue gases of a forced air heating system having a fuel burner by surrounding the flue pipe with a heat exchanger through which heated air is recycled to the heating system, the air being heated in the heat exchanger by heat recovered from the flue gases. However, such previous known heat exchangers are not particularly efficient and require use of an additional blower to cause air to pass through the heat exchanger.
Also, heating air recycled to the heating system from a heat exchanger in contact with hot flue gases may receive toxic gases such as carbon monoxide if the heat exchanger should leak due, for example, to corrosion.
It is therefore an object of the invention to provide an improved heat regulating unit which does not require use of an additional blower to cause air to pass through the heat exchanger.
Another object of the invention is the provision of a heat regulating unit which does not require the recycle of heating air to obviate the risk of introducing toxic gases to the forced air system.
According to the invention, a heat recovery unit for a forced air heating system including a furnace having a fuel burner with a flue pipe for discharge of hot outlet combustion flue gases comprises an elongated metal flue conduit with a flue gas inlet and a flue gas outlet adapted to replace a portion of the flue pipe, an elongated casing surrounding the flue conduit defining an annulus between the casing and the flue conduit, and a heat-absorbing material filling said annulus for absorbing heat from hot flue gases during discharge from the furnace, said heat regulating unit being located in the flue pipe in close proximity to the furnace for transfer of heat from the heat regulating unit back to the furnace when the temperature of the heat regulating unit exceeds the temperature of the furnace.
In a preferred embodiment, the heat regulating unit has a series of equispaced metal fins extending radially outwardly from the flue conduit to the casing defining chambers.
The chambers defined by the series of metal fins may contain a heat-absorbing material packing such as steel wool in contact with the fins and the flue conduit so as to be heated thereby and form a heat sink.